1. Field of the Invention
The present invention relates to a substrate, and particularly to an active device array substrate.
2. Description of Related Art
Among various flat panel displays (FPD), Liquid Crystal Displays (LCDs) have become mainstream in the market due to their advantages such as high space utilization, low power consumption, absence of radiation, and low electromagnetic interference.
FIG. 1A is a perspective view of a conventional liquid crystal display. Referring to FIG. 1A, the conventional liquid crystal display 100 has an active device array substrate 110, an opposite substrate 120, a liquid crystal layer 130 sandwiched between the active device array substrate 110 and the opposite substrate 120, and a backlight module 140 for providing light. The active device array substrate 110 has a plurality of pixel units 112 and a plurality of signal lines 114 located between the pixel units 112. The opposite substrate 120 has a common electrode 122. Liquid crystal molecules in the liquid crystal layer 130 are twisted to certain degree by means of a voltage difference between a pixel electrode 116 in the pixel units 112 and the common electrode 122, such that the transmittance of light L provided by the backlight module 140 passing through a liquid crystal display panel 150 is controlled, and the liquid crystal display panel 150 displays accordingly.
FIG. 1B schematically illustrates an enlarged local cross-sectional view of the conventional liquid crystal display shown in FIG. 1A, wherein a cross-sectional view of two sets of pixel units 112 are shown for illustration. Referring to FIG. 1B, the opposite substrate 120 has a black matrix (BM) 124 (only a black matrix is shown in FIG. 1 for illustration purpose) located above the signal lines 114. As shown in FIG. 1B, since an unexpected twist of the liquid crystal molecules is generated due to the liquid crystal molecules in the liquid crystal layer 130 located above the signal lines 114 being affected by the signal lines 114, such that a light leakage occurs. Therefore, the black matrix 124 is disposed on the opposite substrate 120 located above the signal lines 114 correspondingly, so as to prevent a light leakage by shielding the light that passes through the non-display area (such as an area occupied by the signal lines).
As previously mentioned, when the liquid crystal display 100 displays images, in order to prevent the aforementioned light leakage, the width W′ of the black matrix 124 is widened to reduce a light leakage. However, by widening the width W′ of the black matrix 124, the aperture ratio of the liquid crystal display panel 15 is decreased, such that the brightness of the liquid crystal display 100 is affected. Therefore, it is an important issue to prevent a light leakage while maintaining the aperture ratio of a liquid crystal display.